Tellurium and selenium halide-based glasses, their preparation and use

ABSTRACT

Vitreous solid compositions of formula I: 
     
         Te.sub.w Se.sub.y X.sub.x Z.sub.z                          (I) 
    
     wherein 
     X represents at least one halogen selected from chlorine, bromine and iodine, 
     Z represents at least one element selected from As, Sb and Bi, 
     w, x, y and z represent the molar percentages respectively of elements Te, X, Se and Z, 
     w being a number varying from 5 to 50, 
     x being a number varying from 5 to x 1 , 
     y being a number varying from 5 to 80, 
     z being a number varying from 5 to z 1 , 
     the numbers w, x, y and z being such that the sum (w+x+y+z) is equal to 100, 
     the numbers x 1  and z 1  being such that: 
     when X represents mostly iodine, x 1  =50 and z 1  =60, 
     when X represents mostly bromine, x 1  =60 and z 1  =50, and 
     when X represents mostly chlorine, x 1  =60 and z 1  =40, 
     it being understood that the molar percentage of Bi, when it is present, is not greater than 12 and that the molar percentage of the element Sb, when it is present, is not greater than 20; their preparation and their use principally in the field of infrared transmission.

The present invention has for an object new tellurium halide basedglasses, their preparation and their use principally in the field ofinfrared transmission.

In French patent application 2,594,115, there are described glassesbased on the halide of tellurium and selenium or sulfur which possessgood transmission properties in the infrared. However, these glasseshave relatively low glass transition temperatures which do not permittheir use at high temperatures. Moreover, these glass transitiontemperatures vary only very slightly when the amounts of sulfur orselenium are varied.

It has now been discovered that it is possible to improve the propertiesof glasses based on the halide of tellurium and selenium by the additionof a supplemental constituent such as arsenic, antimony or bismuth.

It has been discovered, in particular, that it is possible to increasethe glass transition temperature by increasing the amount of thissupplemental constituent, and that it even becomes possible to adjustthe glass transition temperature to a predetermined value by regulatingthe amount of the said supplemental constituent. It is thus possible toobtain, because of the invention, glasses based on the halide oftellurium and selenium having glass transition temperatures greater than130° C., and even greater than 150° C., although for glasses based onthe halide of tellurium and sulfur or selenium, the glass transitiontemperature rarely exceeds 80° C.

Moreover, the glasses of the invention are less brittle than glassesbased on the halide of tellurium and selenium. They also exhibit theadvantage of permitting to obtain large pieces by hot pressing, when theglass is in its plasticity zone, at a temperature greater than severaldozens of degrees to the glass transition temperature. These glasses canbe formed by moderate pressure, in pyrex glass enclosures. It has beennoted in effect that the glasses of the invention, thus formed, arecapable of duplicating the polished surface of the pyrex mold, so thatlater the polishing of the piece obtained is not necessary, that whichpermits to considerably lower the cost of production.

Besides, the glasses of the invention can be deposited in thin layers toobtain antireflection deposits or integrated optics. They also permit toeasily produce preforms having double index for the production ofoptical fibers.

The present invention has then for an object vitreous solid compositionsof formula I:

    Te.sub.w Se.sub.y X.sub.x Z.sub.z                          (I)

wherein

X represents at least one halogen selected from chlorine, bromine andiodine,

Z represents at least one element selected from As, Sb and Bi,

w, x, y and z represent the molar percentages respectively of elementsTe, X, Se and Z,

w being a number varying from 5 to 50,

x being a number varying from 5 to x₁,

y being a number varying from 5 to 80,

z being a number varying from 5 to z₁,

the numbers w, x, y and z being such that the sum (w+x+y+z) is equal to100,

the numbers x₁ and z₁ being such that:

when X represents mostly iodine, x₁ =50 and z₁ =60,

when X represents mostly bromine, x₁ =60 and z₁ =50, and

when X represents mostly chlorine, x₁ =60 and z₁ =40,

it being understood that the molar percentage of Bi, when it is present,is not greater than 12 and that the molar percentage of the element Sb,when it is present, is not greater than 20.

The restrictive conditions concerning the maximum amount of antimony andbismuth are conditions generally permitting to obtain glasses by simplecooling of the mixture of constituents in the melted state, withoutrapid cooling (without tempering).

Among the vitreous compositions of the invention, mention can be made inparticular of:

those for which X represents iodine, bromine or their mixtures;

those for which w is a number varying from 10 to 40 and y is a numbervarying from 5 to 65;

those for which z is a number at least equal to 10.

Among the compositions of the invention, certain ones are particularlyinteresting in that their thermal analysis permits to observe nophenomenon linked to a crystallization. In other words, thesecompositions form glasses which are not susceptible to devitrification.Such compositions can be found principally in the following fields:

(a) compositions for which w is a number varying from 15 to 25, x from 5to 15, y from 20 to 60 and z from 10 to 50; and in particular for whichy can vary from 30 to 50 and/or z from 20 to 40; and principally forwhich y can vary from 35 to 45 and/or z can vary from 25 to 35; thesecompositions being principally those for which Z represents mostly As(preferably Z represents As), and in particular those for which Xrepresents mostly iodine (X represents iodine preferably);

(b) compositions for which w can vary from 5 to 20, x from 5 to 15, yfrom 55 to 65 and z from 10 to 25; in particular those for which w canvary from 10 to 20 and/or z can vary from 10 to 20; these compositionsprincipally being those for which Z represents mostly As (preferably Zrepresents As), and in particular those for which X represents mostlyiodine (X representing iodine preferably);

(c) composition for which X represents mostly bromine, w is a numbervarying from 15 to 25, x from 5 to 15, y from 45 to 55 and z from 15 to25, X being bromine preferably, and in particular for which Z representsmostly As (and As preferably).

The invention also has for an object a process for preparing the glasscompositions such as defined above.

This process is characterized by the fact that there is mixed, theamounts indicated by formula I such as defined above, a source oftellurium with a source of halogen, a source of selenium and a source ofelement Z, that the said mixture is heated under an inert atmosphere orunder a vacuum at a temperature sufficient to obtain complete fusion ofthe starting products, that the resulting liquid is maintained at thesaid temperature for a time sufficient to homogenize the said liquidmixture, that, if desired, the said mixture is formed, and that it iscooled so as to obtain a vitreous solid.

As sources of the starting elements, generally these elements themselvesare employed. Also as sources defined compounds containing theseelements can be used. For example, the source of halogen and telluriumcan be TeCl₄, TeBr₄, etc.

Preferably, the preparation is carried out in a sealed tube, afterhaving subjected it to a vacuum. For example, Pyrex glass tubes can beemployed.

The glass can also be transferred to the softened state in a mold, asindicated above, to obtain by moderate pressure a large piece of thedesired form.

The temperature at which the starting product is heated can bedetermined in each case by routine experimentation.

Generally, the mixture of the starting products is heated to atemperature in the order of 300° to about 600° C. For cooling, atempering is generally not necessary. It suffices to let the compositioncool to ambient temperature.

The glass compositions of the invention can also be obtained in the formof thin layers, in particular by cathodic pulverization.

They can, in particular, be fibered and serve as a wave guide for lightemitted by lasers with CO₂. Besides, their wide transmission bandpermits their use in analysis devices of infrared rays or thermalimagery.

The glasses of the invention can principally be deposited in the form ofvitreous thin layers on substrates of varied nature. By cathodicpulverization, guiding structures can be effected with index variationbeing able to make use of wave guide plate for integrated optic, or tocoat optics of clearly inferior index layers with, for example,germanium.

With the glasses of the invention, it is also possible to prepare glasspreforms having double index by one of the two following methods.

According to a first method, a glass bar having a refraction index n₁ isfirst prepared having for example a length of 100 mm and a diameter of 6mm. This bar is inserted in a cylindrical crucible having an innerdiameter slightly greater than the diameter of the glass bar previouslyprepared, for example an inner diameter of 10 mm. The said cruciblecontains a glass according to the invention having an index n₂ (n₂ beingless than n₁), the temperature in the crucible being such that thissecond glass is liquid and viscous. The whole is cooled and a preform isobtained having two indices, and which can then be fibered according toconventional methods.

The second method consists in maintaining the n₁ index bar in the centerof a tube having an inner diameter slightly greater than the diameter ofthe bar, for example 10 mm. Another glass according to the inventionhaving an n₂ index lower than n₁ is then poured into the tube, the saidsecond glass being at a temperature sufficient so that the second glassis in the softened state and can be poured into the tube by filling thespace around the bar. The whole is then cooled as before.

The following nonlimiting examples illustrate the invention.

EXAMPLE 1 Glass having the composition: Te₂₀ Se₆₀ I₁₀ As₁₀

The starting products are purified elements, which are introduced, inthe requisite amounts, in a silica tube. A vacuum is created in theportion of the silica tube situated above the mixture of theconstituents. The tube is then sealed and heated to 350° C. for twohours to obtain good homogenization. The tube is then cooled to ambienttemperature.

The resulting glass has a glass transition temperature, measured bydifferential thermal analysis, with a heating rate of 10° C./m: Tg=80°C.

In a similar manner, glasses containing iodine and having the followingcomposition have been prepared:

    ______________________________________                                        Example Te.sub.w                                                                              Se.sub.x                                                                              I.sub.y                                                                            As.sub.z                                                                            Sb.sub.z                                                                            Tg(°C.)                       ______________________________________                                        2       Te.sub.20                                                                             Se.sub.50                                                                             I.sub.10                                                                           As.sub.20    87                                  3       Te.sub.20                                                                             Se.sub.40                                                                             I.sub.10                                                                           As.sub.30   110                                  4       Te.sub.20                                                                             Se.sub.30                                                                             I.sub.10                                                                           As.sub.40   117                                  5       Te.sub.20                                                                             Se.sub.20                                                                             I.sub.10                                                                           As.sub.50   135                                  6       Te.sub.20                                                                             Se.sub.10                                                                             I.sub.10                                                                           As.sub.60   152                                  7       Te.sub.17                                                                             Se.sub.58                                                                             I.sub.8                                                                            As.sub.17    67                                  8       Te.sub.15                                                                             Se.sub.54                                                                             I.sub.8                                                                            As.sub.23    81                                  9       Te.sub.14                                                                             Se.sub.50                                                                             I.sub.7                                                                            As.sub.29   123                                  10      Te.sub.10                                                                             Se.sub.60                                                                             I.sub.10                                                                           As.sub.20    82                                  11      Te.sub.5                                                                              Se.sub.60                                                                             I.sub.10                                                                           As.sub.25    95                                  12      Te.sub.30                                                                             Se.sub.10                                                                             I.sub.10                                                                           As.sub.50   140                                  13      Te.sub.25                                                                             Se.sub.5                                                                              I.sub.10                                                                           As.sub.60   154                                  14      Te.sub.10                                                                             Se.sub.20                                                                             I.sub.10                                                                           As.sub.60   145                                  15      Te.sub.20                                                                             Se.sub.40                                                                             I.sub.30   Sb.sub.10                                                                            50                                  16      Te.sub.25                                                                             Se.sub.40                                                                             I.sub.30   Sb.sub.5                                                                             61                                  17      Te.sub.20                                                                             Se.sub.50                                                                             I.sub.10   Sb.sub.20                                                                            80                                  ______________________________________                                    

In a similar manner, glasses having the following composition have beenprepared:

    ______________________________________                                        Te.sub.20    Se.sub.60  I.sub.10  Sb.sub.10                                   Te.sub.35    Se.sub.25  I.sub.20  As.sub.20                                   Te.sub.35    Se.sub.40  I.sub.5   As.sub.20                                   Te.sub.30    Se.sub.20  I.sub.30  As.sub.20                                   Te.sub.10    Se.sub.60  I.sub.10  As.sub.20                                   Te.sub.10    Se.sub.20  I.sub.10  As.sub.60                                   ______________________________________                                    

In a similar manner, glasses containing bromine and having the followingcomposition have been prepared.

    ______________________________________                                        Example Te.sub.w                                                                              Se.sub.x                                                                              Br.sub.y                                                                           As.sub.z                                                                            Bi.sub.z                                                                            Tg(°C.)                       ______________________________________                                        18      Te.sub.20                                                                             Se.sub.50                                                                             Br.sub.10                                                                          As.sub.40   115                                  19      Te.sub.20                                                                             Se.sub.50                                                                             Br.sub.10                                                                          As.sub.20   89                                   20      Te.sub.20                                                                             Se.sub.40                                                                             Br.sub.10                                                                          As.sub.30   107                                  21      Te.sub.20                                                                             Se.sub.20                                                                             Br.sub.10                                                                          As.sub.50   129                                  22      Te.sub.20                                                                             Se.sub.60                                                                             Br.sub.10                                                                          As.sub.10   80                                   23      Te.sub.18                                                                             Se.sub.64                                                                             Br.sub.9                                                                           As.sub.9    70                                   24      Te.sub.18                                                                             Se.sub.46                                                                             Br.sub.18                                                                          As.sub.18   83                                   25      Te.sub.23                                                                             Se.sub.49                                                                             Br.sub.23  Bi.sub.5                                                                            70                                   26      Te.sub.36                                                                             Se.sub.27                                                                             Br.sub.27  Bi.sub.10                                                                           75                                   ______________________________________                                    

In a similar manner, glasses containing chlorine and having thefollowing composition have been prepared:

    ______________________________________                                        Example   Te.sub.w                                                                              Se.sub.x                                                                              Cl.sub.y                                                                            As.sub.z                                                                           Tg(°C.)                           ______________________________________                                        27        Te.sub.20                                                                             Se.sub.60                                                                             Cl.sub.10                                                                           As.sub.10                                                                           90                                      28        Te.sub.20                                                                             Se.sub.50                                                                             Cl.sub.10                                                                           As.sub.20                                                                          104                                      29        Te.sub.20                                                                             Se.sub.40                                                                             Cl.sub.10                                                                           As.sub.30                                                                          122                                      ______________________________________                                    

To introduce the chlorine into the starting mixture, the requisiteamount of chlorine is reacted with the Te+Se+As mixture. There can alsobe used, as a source of chlorine, at least one chloride of these threeelements, in the anhydrous state, in a suitable amount.

We claim:
 1. Solid vitreous compositions of formula I:

    Te.sub.w Se.sub.y X.sub.x Z.sub.z                          (I)

wherein X represents at least one halogen selected from chlorine,bromine and iodine, Z represents at least one element selected from As,Sb and Bi, w, x, y and z represent the molar percentages respectively ofthe elements Te, X, Se and Z, w being a number varying from 10 to 40, xbeing a number varying from 5 to x₁, y being a number varying from 5 to65, z being a number varying from 5 to z₁, the numbers w, x, y and zbeing such that the sum (w+x+y+z) is equal to 100, the numbers x₁ and z₁being such that: when X represents greater than 50% iodine, x₁ =50 andz₁ =60, when X represents greater than 50% bromine, x₁ =60 and z₁ =50,and when X represents greater than 50% chlorine, x₁ =60 and z₁ =40, itbeing understood that the molar percentage of Bi, when it is present, isnot greater than 12 and that the molar percentage of the element Sb,when it is present, is not greater than
 20. 2. Vitreous compositionsaccording to claim 1, characterized by the fact that X representsiodine, bromine or their mixtures.
 3. Compositions according to claim 1,characterized by the fact that z is a number at least equal to
 10. 4.Compositions according to claim 3, characterized by the fact that w is anumber varying from 15 to 25, x from 5 to 15, y from 20 to 60, and zfrom 10 to
 50. 5. Compositions according to claim 4, characterized bythe fact that y can vary from 30 to 50 and/or z from 20 to
 40. 6.Compositions according to claim 4, characterized by the fact that y canvary from 35 to 45 and/or z can vary from 25 to
 35. 7. Compositionsaccording to claim 3, characterized by the fact that w can vary from 10to 20, x from 5 to 15, y from 55 to 65 and z from 10 to
 25. 8.Compositions according to claim 7, characterized by the fact that w canvary from 10 to 20 and/or z can vary from 10 to
 20. 9. Compositionsaccording to claim 3, characterized by the fact that w can vary from 10to 20, x from 15 to 25, y from 25 to 35 and z from 30 to
 40. 10.Composition according to claim 1, characterized by the fact that Zrepresent greater than 50% As.
 11. Compositions according to claim 10,characterized by the fact that Z represents As.
 12. Compositionsaccording to claim 1, characterized by the fact that X representsgreater than 50% iodine.
 13. Compositions according to claim 12,characterized by the fact that X represent iodine.
 14. Compositionsaccording to claim 3, characterized by the fact that X representsgreater than 50% bromine, w is a number varying from 15 to 25, x from 5to 15, y from 45 to 55 and z from 15 to
 25. 15. Compositions accordingto claim 14, characterized by the fact that X represents bromine. 16.Compositions according to claim 14, characterized by the fact that Zrepresents greater than 50% As.
 17. Process for preparing vitreouscompositions such as defined in claim 1, characterized by the fact thatone mixes, in the amounts indicated by formula I, a source of telluriumwith a source of halogen, a source of selenium, and a source of theelement Z, that one heats the said mixture in an inert atmosphere orunder a vacuum to a temperature sufficient to obtain a complete fusionof the starting products, that one maintains the resulting liquid atsaid temperature for a time sufficient to homogenize the liquid mixture,that, if desired, one puts it into a form, and that one cools it toobtain a vitreous solid.
 18. Process according to claim 17,characterized by the fact that the forming step comprises transferringit in a mold to obtain by moderate pressure a large piece of the desiredform.
 19. Process according to claim 17, characterized by the fact that,to obtain a glass preform having a double index, one prepares a glassbar that one places in the center of a cylindrical crucible having aninterior diameter greater than the diameter of the bar, the saidcrucible containing, in the liquid and viscous state, a glass having anindex lower than that of said glass bar, and that one lets the whole tocool.
 20. Process according to claim 17, characterized by the fact that,to obtain a glass preform having a double index, one prepares a glassbar that one places at the center of a cylindrical crucible having aninterior diameter greater than the diameter of the bar, that one poursinto the crucible a second glass having a lower index, in the softenedstate, so that it fills the space around the bar, and that one lets thewhole to cool.